Thermosetting resin compositions and their use for making resin articles and thin film wiring boards

Abstract: The invention relates to a thermosetting resin composition comprising (A) a thermosetting polyimide and (B) a bismaleimide and showing a modulus of elasticity of 10² to 10⁷ dyne/cm² in the course of heat curing step which is suitable for forming adhesive films used in thin film wiring boards having excellent heat resistance and high reliability. The invention further relates to precursor compounds and compositions.

Description: This invention relates to thermosetting resin compositions suitable as materials for electrical apparatuses and electronic parts and comprising a polyimide having no thermoplastic property and a thermosetting prepolymer, these compositions showing a modulus of elasticity of 10 7 to 10 2 dyne/cm 2 in the course of the heat curing step, and the use of these thermosetting resin compositions as adhesive layers in thin film wiring boards, and resin articles obtained from these compositions. Heretofore, there have been disclosed thin film multi-layer wiring boards obtained by laminating a plurality of thin film material layers having wiring patterns thereon and a plurality of adhesive films present between thin film material layers (JP-A-2-45998). Further, JP-A-4-206595 discloses a process for producing a thin film multi-layer wiring board comprising laminating a plurality of thin film material layers having wiring patterns thereon via adhesive films and connecting individual wiring layers by laser drilling and plating. As adhesives for wiring boards, there have been disclosed thermosetting resin compositions obtained by adding bismaleimides to special polyimides (JP-A 59-179558, 62-11662, EP-A-0342912 etc.) however, the polyimides used therein are thermoplastic polyimides such as Polyimide 2080 (a trade name, mfd. by Mitsubishi Chemical Co., Ltd.). Further, there are also disclosed adhesives obtained by adding thermosetting prepolymers to polyimides having low softening points (JP-A 2-124971 and 2-247,273). The polyimides used therein belong to thermoplastic polyimides according to M.I. Bessonov, et al.(M.I. Bessonov, M.M. Koton, V.V. Kudryavtsev and L.A. Laius: "Polyimides", pp. 185-199, (1987), published by Plenum Publishing Corp., New York). Since the adhesives used in the above-mentioned thin film multi-layer wiring -boards became brittle, there was a problem in reliability regarding the practical use in wiring boards, resulting in failing to produce thin film wiring boards having sufficient reliability. Further, the adhesives used in the production of thin film multi-layer wiring boards had problems concerning the burying of the wiring so as to obtain good surface flatness and heat resistance, also resulting in failing to produce thin film wiring boards having sufficient reliability. The adhesives used in the prior art were thermoplastic polyimides having good adhesiveness to adherends and good flowability. However, according to the prior art processes, since the thermoplastic polyimides are low in modulus of elasticity at the glass transition temperature or higher due to softening with heating, there arised troubles such as deformation of adhesive portions and cutting of wirings during soldering in the production of large scale integrated circuits (LSI). Further, since the dimensional change rate of thermoplastic polyimides used at or above the glass transition temperature is large and the relative positions between wirings change extremely, there result great troubles when planning a higher density of wiring. It is the object of the present invention to provide special thermosetting resin compositions excellent in heat resistance and molding properties and having excellent adhesiveness to resins, ceramics, etc., corresponding intermediate compounds, and their use, particularly for manufacturing thin film wiring boards having high reliability wherein these resins are used as adhesives. The above object is achieved according to the independent claims. The dependent claims relate to preferred embodiments. The present invention provides thermosetting resin compositions comprising (A) a polyimide component comprising or consisting of: a thermosetting polyimide having repeating units of the formula I wherein are: R an alkyl group, a fluorinated alkyl group, an alkoxy group, a fluorinated alkoxy group, or a halogen atom; n 0, 1 or 2, and m 0 or an integer of 1 to 4, the polyimide having repeating units of the formula I being present in an amount of 30 % by weight or more, and preferably 50 % by weight or more, based on the weight of the polyimide component (A), (B) a bismaleimide compound of the formula II wherein Ar is a divalent organic group having at least two carbon atoms. According to a preferred embodiment, the thermosetting resin composition shows a modulus of elasticity of 10 2 to 10 7 dyne/cm 2 in the course of heat curing. According to another preferred embodiment, the bismaleimide compound (B) is represented by the formula III wherein R 1 through R 6 are independently H, CH 3 , C 2 H 5 , C 3 H 7 , F, CF 3 , C 2 F 5 or C 3 F 7 ; and m is zero or an integer of 1 to 4, and the individual indices m may be the same or different. The components (A) and (B) are preferably mixed in amounts of 100 parts by weight of the component (A) and 50 to 200 parts by weight of the component (B). The component (A) is preferably prepared by reacting pyromellitic dianhydride with diaminodiphenylether in an organic solvent. In accordance with another preferred embodiment, the polyimide component (A) comprises or consists of: (a) a polyimide having repeating units of the formula V and (b) a polyimide having repeating units of the formula VI According to yet another preferred embodiment, the polyimide component (A) further comprises a polyimide having repeating units of the formula IV wherein R and n are as defined in formula I, the polyimide having repeating units of the formula IV being preferably present in an amount of 1 to 20 % by weight, based on the total weight of the polyimide component (A). The polyimide is preferably obtained by adding a poly(amic acid) to the bismaleimide (B), followed by imidization. In accordance with another aspect of the present invention, thermosetting resin compositions are provided which comprise (A') a poly(amic acid) component comprising or consisting of a precursor compound which is a poly(amic acid) obtained by reaction of a tetracarboxylic acid anhydride of the formula VII wherein R is an alkyl group, a fluorinated alkyl group, an alkoxy group, a fluorinated alkoxy group, or a halogen atom, and n is 0, 1 or 2, with a 4,4'-diaminodiphenyl ether of the formula VIII wherein R is as defined above, and m is 0 or an integer of 1 to 4, and (B) a bismaleimide compound of formula II as defined above. Also in the case of the precursor compositions, the bismaleimide compound (B) is preferably represented by the formula III as defined above. In accordance with a preferred embodiment, the poly(amic acid) component (A') comprises or consists of (a') a poly(amic acid) obtained by reaction of pyromellitic acid dianhydride with 4,4'-diaminodiphenylether and (b') a poly(amic acid) obtained by reaction of 3,3',4,4'-tetracarboxybenzophenone with 4,4'-diaminodiphenylether. The poly(amic acid) component (A') may preferably further comprise a poly(amic acid) obtained by reaction of the tetracarboxylic acid anhydride of formula VII as defined above with 4,4'-diaminodiphenylether-3-carbonamide of the formula preferably in an amount of 0.01 to 0.2 equivalent weight per equivalent weight of the tetracarboxylic acid dianhydride. The components (A) and (B), or the components (A') and (B), respectively, of the resin compositions according to the invention may be present in the form of a mixture thereof; alternatively, the components (A) and (B), or the components (A') and (B), respectively, may be present separately in the form of a kit of parts, one part comprising component (A) or (A'), and the other part comprising the component (B). The invention further relates to the use of the thermosetting resin compositions as defined above for manufacturing thin film wiring boards. The thin film wiring boards of the present invention comprise a plurality of base films having wiring patterns thereon and one or more adhesive layers placed between the base films, wherein the adhesive layers are made from a thermosetting resin composition as defined above. In particular, the present invention deals with thin film wiring boards as defined above, wherein the polyimide is obtained from a poly(amic acid) by imidization. Finally, the present invention pertains to resin articles obtained from the thermosetting compositions as defined above by curing. DESCRIPTION OF PREFERRED EMBODIMENTS According to the present invention, a thin film wiring board having high reliability can be obtained by using an adhesive layer made from a thermosetting resin composition comprising (A) a thermosetting polyimide containing repeating units of the formula I wherein R is an alkyl group preferably having 1 to 6 carbon atoms, a fluorinated alkyl group preferably having 1 to 6 carbon atoms, an alkoxy group preferably having 1 to 6 carbon atoms, a fluorinated alkoxy group preferably having 1 to 6 carbon atoms or a halogen atom such as F, Cl, Br or I; n is zero or an integer of 1 or 2; and m is zero or an integer of 1 to 4, in an amount of 30% by weight or more, based on the weight of the polyimide, and (B) a bismaleimide compound of the formula II wherein Ar is a divalent organic group having at least two carbon atoms, for example, an aromatic group such as a phenylene group, an alkyl group, an ether group, a fluorinated alkyl group, or a combination of these groups, said thermosetting resin composition showing a modulus of elasticity of 10 7 to 10 2 dyne/cm 2 in the course of heat curing step. When a thermosetting resin is used, it is inevitable to make the resin molten and adhered to an adherend and to deform it during curing in order to obtain good adhesiveness and moldability. From the viewpoint of melt flow, it is better to use a thermoplastic polyimide. But when the thermoplastic polyimide is used, the modulus of elasticity of the polyimide after curing is undesirably lowered above the glass transition temperature of the polyimide used. In order to solve such a problem, the flow phenomenon of the resin during curing was studied earnestly. As a result, it was found that the flowing of the resin comprises a step of a prepolymer melting phenomenon with the temperature rise with heating, and a step of melt flow of the polyimide formed by the molten prepolymer. From the above-mentioned viewpoint, various combinations of prepolymers and polyimides were studied. As a result, it was found surprisingly that, although the polyimide having repeating units of the formula I did not have thermoplast properties when used singly, said polyimide melted well with a molten prepolymer and had a largely lowered modulus of elasticity compared with the case of single use, and a processing window. The term "processing window" means that a thermosetting resin has a temperature range and a time range from softening of the resin until curing of the resin in the course of curing of the resin. That is, when a resin has a processing window, it is suitable for adhesives and molding materials. As the prepolymer, it was found that the bismaleimide of the formula II was suitable and particularly well compatible with the above-mentioned polyimide. The thermosetting composition comprising the polyimide having repeating units of the formula I and the bismaleimide of the formula II has a modulus of elasticity of 10 6 dyne/cm 2 or more at 300°C, which value is not expected from the adhesive of JP-A 2-124,971 comprising a thermoplastic polyimide and a bismaleimide. In addition, the thermosetting resin composition of the present invention shows a modulus of elasticity of as largely low as 10 2 to 10 7 dyne/cm 2 in the course of heat curing. This means that the adhesiveness to an adherend can be greatly improved. Further, when a bismaleimide (B) of the formula III as defined above is used in combination with the polyimide having repeating units of the formula I, better results can be obtained. That is, in the course of curing, the thermosetting resin composition flows in a uniformly molten state and sticks to an adherend to give excellent adhesiveness. Further, after curing, the lowering in the modulus of elasticity is small even at high temperatures of 300°C or higher, and the mechanical strength is large. By using such a thermosetting resin composition as an adhesive layer, there can be obtained thin film wiring boards having excellent heat resistance, for example, soldering heat resistance of 300°C or higher. In the case of using 2,2-bis[4-(4-maleimidophenoxy)-phenyl]propane as the maleimide of the formula III, the curing temperature becomes sufficient at 250°C or lower, known curing apparatuses and conditions can be used without modification, and the raw materials can be obtained at relatively low cost. In the case of using 2,2-bis[4-(4-maleimidophenoxy)-phenyl]-1,1,1,3,3,3-hexafluoropropane as the maleimide of the formula III, the flow properties during curing and the moldability are particularly excellent, resulting in easily sticking surfaces with fine relief or holes without voids. More concretely, when a pair of wiring sheets having holes of 20 µm in diameter and 50 µm in depth and wirings of 50 µm in width and 50 µm in height thereon are mounted facing each other via a thermosetting resin film mentioned above and pressed, there can be obtained adhesive layer structures the cross-section of which has no voids. In the case of using a bismaleimide having 2,2-bis[4-(4-maleimidophenoxy)-phenyl]-1,1,1,3,3,3-hexafluoropropane as a skeleton and much more fluorine atoms attached thereto as the maleimide of the formula III, the dielectric constant of the thermosetting resin composition can be lowered. When such thermosetting resin compositions are used as electronic materials, the transmission rate of signals can be improved. The polyimide having repeating units of the formula I is preferably a reaction product of a tetracarboxylic acid dianhydride and a diaminodiphenyl ether. Examples of the tetracarboxylic acid dianhydride are pyromellitic dianhydride, 3-methylpyromellitic dianhydride, 3-trifluoromethylpyromellitic dianhydride, etc. Examples of the diaminodiphenyl ether are diaminodiphenyl ether, 2,2'-dimethyl-4,4'-diaminodiphenyl ether, 2,2'-trifluoromethyl-4,4'-diaminodiphenyl ether, 3,3'-di-methyl-4,4'-diaminodiphenyl ether, 3,3'-bis(trifluoromethyl)-4,4'-diaminodiphenyl ether, etc. The polyimide having repeating units of the formula I can be prepared by dehydration condensation with heating of, for example, pyromellitic dianhydride with diaminodiphenyl ether in an organic solvent such as diaminoacetamide, dimethylacetamide, dimethylformamide, N-methyl-2-pyrrolidone, etc. according to a conventional process. As the polyimide (A), it is possible to use other polyimides obtained by reacting an acid component such as a tetracarboxylic acid dianhydride with an aromatic diamine together with the polyimide having repeating units of the formula I. As the acid component, there can be used tetracarboxylic acids, esters thereof, acid dianhydrides, and acid chlorides. Examples of the tetracarboxylic acid compounds are 2,3,3',4'-tetracarboxydiphenyl, 3,3',4,4'-tetracarboxydiphenyl, 3,3',4,4'-tetracarboxydiphenyl ether, 2,3,3',4'-tetracarboxydiphenyl ether, 3,3',4,4'-tetracarboxybenzophenone, 2,3,3'-4'-tetracarboxybenzophenone, 2,3,6,7-tetracarboxynaphthalene, 1,4,5,7-tetracarboxynaphthalene, 1,2,5,6-tetracarboxynaphthalene, 3,3',4,4'-tetracarboxydiphenylmethane, 2,2-bis(3,4-dicarboxyphenyl)propane, 3,3',4,4'-tetracarboxydiphenylsulfone, 3,4,9,10-tetracarboxyperylene, 2,2-bis[4-(3,4-dicarboxyphenoxy)-phenyl]propane, 2,2-bis[4-(3,4-dicarboxyphenoxy)-phenyl]hexafluoropropane, butanetetracarboxylic acid, etc. These tetracarboxylic acid compounds can be used singly or as a mixture thereof. As the aromatic diamines, there can be used p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminophenylsulfide, 4,4'-diaminodiphenylsulfone, 4,4'-diaminodiphenylketone, 4,4'-diaminodiphenylpropane, etc. It is also possible to use as the diamine 4,4'-diaminodiphenylether-3-carbonamide of the formula: preferably in an amount of 0.01 to 0.2 equivalent weight per equivalent weight of the tetracarboxylic dianhydride. By the use of 4,4'-diaminodiphenylether3-carboxamide, the heat resistance of the thermosetting resin composition after curing can be improved without damaging the flowability at the time of curing. When 4,4'-diaminodiphenylether-3-carbonamide is used, a polyimide having repeating units of the formula IV wherein R and n are as defined above, is obtained. It is preferable to use the polyimide having repeating units of the formula IV in an amount of 1 to 20% by weight, based on the total weight of the polyimides, in addition to the polyimide having the repeating units of the formula I. Further, it is preferable to use polyimides having the following repeating units V and VI: In such a case, the use of polyimides having repeating units of the formula IV in an amount of 1 to 20% by weight, based on the total weight of the polyimides, together with the polyimides having the repeating units of the formulae V and VI is also preferable. The polyimide having repeating units of the formula I can be used in admixture with other polyimides mentioned above, or at least one of the polyimides can be mixed in the state of polyimide precursor (i.e., poly(amic acid) polymer). A preferable example of a commercially available polyimide precursor is PIQ (a trade name, mfd. by Hitachi Chemical Co., Ltd.). In any case, the polyimide having repeating units of the formula I must be contained in an amount of 30% by weight or more, preferably 50% by weight or more, based on the total weight of the polyimide component (A). The bismaleimide compounds of the formula II which can be used as N,N'-substituted unsaturated imides, are addition type bismaleimides including bifunctional maleimides, polyfunctional maleimides and reaction product type maleimides. Examples of bifunctional bismaleimides are as follows: N,N'-ethylenedimaleimide, N,N'-hexamethylenebismaleimide, N,N'-dodecamethylenebismaleimide, N,N'-m-xylylenebismaleimide, N,N'-p-xylylenedimaleimide, N,N'-1,3-bismethylenecyclohexanebismaleimide, N,N'-1,4-bismethylenecyclohexanebismaleimide, N,N'-2,4-tolylenebismaleimide, N,N'-2,6-tolylenebismaleimide, N,N'-3,3-diphenylmethanebismaleimide, N,N'-4,4-diphenylmethanebismaleimide, 3,3'-diphenylsulfonebismaleimide, 4,4'-diphenylsulfonebismaleimide, N,N'-4,4'-diphenylsulfidebismaleimide, N,N'-p-benzophenonebismaleimide, N,N'-diphenylethanebismaleimide, N,N'-diphenylether bismaleimide, N,N'-(methylene-ditetrahydrophenyl)-bismaleimide, N,N'-3-ethyl-4,4'-diphenylmethanebismaleimide, N,N'-3,3'-dimethyl-4,4'-diphenylmethanebismaleimide, N,N'-3,3'-diethyl-4,4'-diphenylmethanebismaleimide, N,N'-3,3'-dichloro-4,4'-diphenylmethanebismaleimide, N,N'-tolidinebismaleimide, N,N'-isophoronebismaleimide, N,N'-p,p'-diphenyldimethylsilylbismaleimide, N,N'-benzophenonebismaleimide, N,N'-diphenylpropanebismaleimide, N,N'-naphthalenebismaleimide, N,N'-m-phenylenebismaleimide, N,N'-4,4'-(1,1-diphenyl-cyclohexane)bismaleimide, N,N'-3,5-(1,2,4-triazole)-bismaleimide, N,N'-pyridine-2,6-diylbismaleimide, N,N'-5-methoxy-1,3-phenylenebismaleimide, 1,2-bis(2-maleimidoethoxy)ethane, 1,3-bis(3-maleimidopropoxy)propane, bis(3-ethyl-4-maleimido-5-methylphenyl)methane, N,N'-4,4'-diphenylmethane-bis-dimethylmaleimide, N,N'-hexamethylene-bis-dimethylmaleimide, N,N'-4,4'-(diphenylether)-bis-dimethylmaleimide, N,N'-4,4'-(diphenylsulfone)-bis-dimethylmaleimide, N,N'-bismaleimide of N,N'-4,4'-(diamino)triphenylphosphate, etc. Examples of polyfunctional maleimides are reaction products of aniline with formaldehyde (polyamine compounds), reaction products of 3,4,4'-triaminodiphenylmethane or triaminophenol with maleic anhydride, etc. Examples of reaction product type maleimides are reaction products of tris(4-aminophenyl)phosphate, tris(4-aminophenyl)phosphate, or tris(4-aminophenyl)thiophosphate with maleic anhydride, etc. Examples of the compounds of the formula III, which are particularly preferable compounds among those of the formula II, are as follows: 2,2-bis[4-(4-maleimidophenoxy)-phenyl]propane, 2,2-bis[3-methyl-4-(4-maleimidophenoxy)phenyl]propane, 2,2-bis[3-chloro-4-(4-maleimidophenoxy)phenyl]propane, 2,2-bis[3-bromo-4-(4-maleimidophenoxy)-phenyl]-propane, 2,2-bis[3-ethyl-4-(4-maleimidophenoxy)-phenyl]propane, 2,2-bis[3-propyl-4-(4-maleimidophenoxy)phenyl]propane, 2,2-bis[3-isopropyl-4-(4-maleimidophenoxy)phenyl]propane, 2,2-bis[3-butyl-4-(4-maleimidophenoxy)-phenyl]propane, 2,2-bis[3-sec-butyl-4-(4-maleimidophenoxy)-phenyl]propane, 2,2-bis[3-methoxy-4-(4-maleimidophenoxy)phenyl]propane, 1,1-bis[4-(4-maleimidophenoxy)-phenyl]ethane, 1,1-bis[3-methyl-4-(4-maleimidophenoxy)phenyl]ethane, 1,1-bis[3-chloro-4-(4-maleimidophenoxy)phenyl]ethane, 1,1-bis[3-bromo-4-(4-maleimidophenoxy)phenyl]ethane, bis[4-(4-maleimidophenoxy)-phenyl]methane, bis[3-methyl-4-(4-maleimidophenoxy)-phenyl]methane, bis[3-chloro-4-(4-maleimidophenoxy)-phenyl]methane, bis[3-bromo-4-(4-maleimidophenoxy)-phenyl]methane, 1,1,1,3,3,3-hexachloro-2,2-bis[4-(4maleimidophenoxy)-phenyl]propane, 3,3-bis[4-(4-maleimidophenoxy)-phenyl]pentane, 1,1-bis[4-(4-maleimidophenoxy)-phenyl]propane, 2,2-bis[3,5-dimethyl-4-(4-maleimidophenoxy)phenyl]propane, 2,2-bis[3-fluro-4-(4-maleimidophenoxy)-phenyl]propane, 2,2-bis[3-trifluoromethyl-4-(4-maleimidophenoxy)-phenyl]propane, 2,2-bis[3-perfluoropropyl-4-(4-maleimidophenoxy)-phenyl]propane, 2,2-bis[4-(3-methyl-4-maleimidophenoxy)phenyl]propane, 2,2-bis[3-methyl-4-(3,5-dimethyl-4-maleimidophenoxy)-phenyl]propane, 2,2-bis[3-propyl-4-(3-fluoro-4-maleimidophenoxy)-phenyl]propane, 2,2-bis[3,5-dimethyl-4-(3-trifluoromethyl-4-maleimidophenoxy)-phenyl]propane, 2,2-bis[3-fluoro-4-(3-perfluoropropane-4-maleimidophenoxy)-phenyl]propane, 2,2-bis[3-trifluoromethyl-4-(3-trifluoromethyl-4-maleimidophenoxy)-phenyl]propane, etc. Examples of bismaleimides having a 2,2-bis[4-(4-maleimidophenoxy)-phenyl]-1,1,1,3,3,3-hexafluoropropane skeleton among the bismaleimides of the formula III are as follows: 1,1,1,3,3,3-hexafluoro-2,2-bis[4-(4-maleimidophenoxy)-phenyl]propane, 1,1,1,3,3,3-hexafluoro-2,2-bis[3,5-dimethyl-4-(4-maleimidophenoxy)-phenyl]propane, 1,1,1,3,3,3-hexafluoro-2,2-bis[3,5-dibromo-4-(4-maleimidophenoxy)-phenyl]propane, 1,1,1,3,3,3-hexafluoro-2,2-bis[3-methyl-4-(4-maleimidophenoxy)-phenyl]propane, 1,1,1,3,3,3-hexafluoro-2,2-bis[3-propyl-4-(4-maleimidophenoxy)-phenyl]propane, 1,1,1,3,3,3-hexafluoro-2,2-bis[3-fluoro-4-(4-maleimidophenoxy)-phenyl]propane, 1,1,1,3,3,3-hexafluoro-2,2-bis[3-pefluoropropyl-4-(4-maleimidophenoxy)-phenyl]propane, 1,1,1-3,3,3-hexafluoro-2,2-bis[3-trifluoromethyl-4-(4-maleimidophenoxy)-phenyl]propane, 1,1,1,3,3,3-hexafluoro-2,2-bis[3,5-ditrifluoromethyl-4-(4-maleimidophenoxy)-phenyl]propane, 1,1,1,3,3,3-hexafluoro-2,2-bis[4-(3-methyl-4-maleimidophenoxy)-phenyl]propane, 1,1,1,3,3,3-hexafluoro-2,2-bis[3-methyl-4-(3,5-dimethyl-4-maleimidophenoxy)-phenyl]propane, 1,1,1,3,3,3-hexafluoro-2,2-bis[3-propyl-4-(3-fluoro-4-maleimidophenoxy)-phenyl]propane, 1,1,1,3,3,3-hexafluoro-2,2-bis[3-fluoro-4-(3-perfluoropropyl-4-maleimidophenoxy)-phenyl]propane, 1,1,1,3,3,3-hexafluoro-2,2-bis[3,5-ditrifluoromethyl-4-(3,5-ditrifluoromethyl-4-maleimidophenoxy)-phenyl]propane, etc. The thermosetting resin composition of the present invention comprises (A) a thermosetting polyimide containing repeating units of the formula I in an amount of 30% by weight or more, based on the weight of the polyimide, and (B) a bismaleimide compound of the formula II. The polyimide (A) is thermosetting. The composition has a modulus of elasticity of preferably 10 5 dyne/cm 2 or more at 300°C, and is hardly soluble in organic solvents. The thermosetting resin composition can be prepared by (i) preparing a varnish of poly(amic acid) which is a precursor of the polyimide having repeating units of the formula I, mixing with a bismaleimide of the formula II, and carrying out imidization with heating, (ii) mixing the polyimide with the bismaleimide in powder state, and preferably in molten state, or the like conventional methods. The thermosetting resin composition may further contain one or more other polymers and fillers so long as the desired properties are not reduced. For example, it is possible that it contains one or more thermosetting prepolymers in addition to 2,2-bis[4-(4-maleimideophenoxy)-phenyl]propane, or 2,2-bis[4-(4-maleimidophenoxy)-phenyl]-1,1,1,3,3,3-hexafluoropropane, so long as the desired properties are not reduced. If necessary, a radical generator can be mixed so as to lower the curing temperature. The mixing ratio of the polyimide (A) and the bismaleimide (B) in the thermosetting resin composition is preferably 100 parts by weight of the polyimide (A) and 50 to 200 parts by weight of the bismaleimide (B). When the amount of the bismaleimide (B) is lower than 50 parts by weight, uniform melting of (A) and (B) during curing becomes difficult, resulting in lowering adhesiveness and moldability. On the other hand, when the amount of the bismaleimide (B) is more than 200 parts by weight, heat resistance and mechanical strength of the cured product are undesirably lowered. Further, when the proportion of the polyimide having repeating units of the formula I becomes lower than 30% by weight, based on the total weight of polyimide component, the adhesiveness and the modulus of elasticity at high temperatures are undesirably lowered. By using the thermosetting resin composition in the adhesive layer in thin film wiring boards, the resulting thin film wiring boards show excellent heat resistance. Further, since the thermosetting resin composition shows a modulus of elasticity of 10 2 to 10 7 dyne/cm 2 in the course of the heat curing step, there can be obtained an excellent adhesive strength between the resin and conductors such as copper as high as 0.5 to 2.0 kg/cm and good burying property of wiring in the resin (adhesive) layer so as to obtain good surface flatness without causing level differences. The thin film wiring boards of the present invention can be produced, without influences of the use of the thermosetting resin composition, by conventional methods for producing conductors such as etching, electroless plating, electric plating, evaporation, sputtering, etc. The thin film wiring boards can be effectively used as a package for logic elements and module substrate, etc. in large-scale computers, super computers, work stations, etc. The present invention is illustrated by way of the following Examples, in which all amounts in percents are by weight. Example 1 In a 2000-ml three-necked flask equipped with a stirrer, 143.6 g of 4',4'-diaminodiphenylether (DDE) and 700 ml of N-methyl-2-pyrrolidone (NMP) were placed and dissolved. Then, 156.4 g of pyromellitic dianhydride were gradually added to the flask to carry out the reaction with stirring at -5°C to room temperature for 6 hours to give a varnish of poly(amic acid) (1) (solid content: 30%, reduced viscosity: 0.95 dl/g at 25°C in N-methylpyrrolidone). Then, an NMP solution containing 113.1 g of 2,2-bis[4-(4-maleimidophenoxy)-phenyl]-1,1,1,3,3,3-hexafluoropropane (6FDAPP-BMI) was added to the poly(amic acid) varnish (1) and mixed and dissolved at room temperature to give a varnish (1-a) (solid content: 30%). The proportion of 6FDAPP-BMI (solid content) in the total solid was made 40%. The varnish (1-a) was coated on a polyimide film (Upilex R film, a trade name, mfd. by Ube Industries, Ltd.) of 0.1 mm thickness and heated in a constant temperature bath (conditions: 100°C/60 min + 200°C/30 min) to give an imide film (1-b). The imide film (1-b) was pealed off from the Upilex R film and subjected to a heat press treatment (conditions: 270°C/50 min, pressure 30 kg/mm 2 ) using a press to give an imide film (1-c). The imide films (1-b) and (1-c) were subjected to measurement of the modulus of elasticity using a viscoelasticity tester (DVE-V4 type, mfd. by Rheology Co., Ltd.) under the following conditions: Length of specimen 30 mm Chuck distance 20 mm Sinusoidal strain displacement under continuous vibration 0.0005 mm Automatic static loading Frequency 5 Hz Temperature rise 2°C/min Further, using a tensile strength tester, breaking strain and breaking strength were measured under the following conditions: Length of specimen 60 mm Chuck distance 40 mm Tensile speed 5 mm/min Room temperature Further, the pealing strength was measured at a copper foil surface and polyimide surface. The results are shown in Table 1. Examples 2 to 4 Films (1-b) and (1-c) were produced in the same manner as described in Example 1, except for changing the proportion of 6FDAPP-BMI (solid content) in the varnish (1-a) (total solid content) to 30%, 50% and 65%. The properties of the films were evaluated in the same manner as described in Example 1 and are listed in Table 1. Example 5 A polyimide obtained from 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride and 2,2-bis[4-(p-aminophenoxy)-phenyl]propane in the same manner as described in Example 1 was used in place of 30% of the polyimide of Example 2. The properties of the resulting films were evaluated in the same manner as described in Example 1 and are listed in Table 1. Example 6 A polyimide obtained from 3,3',4,4'-biphenyltetracarboxylic acid dianhyride and diaminodiphenylether in the same manner as described in Example 1 was used in place of 50% of the polyimide of Example 2. The properties of the resulting films were evaluated in the same manner as described in Example 1 and are listed in Table 1. Example 7 The process of Example 1 was repeated except for using 2,2-bis[4-(4-maleimidophenoxy)-phenyl]propane in place of 50% of 2,2-bis[4-(4-maleimidophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane. The properties of the resulting films were evaluated in the same manner as described in Example 1 and are listed in Table 1. Example 8 The process of Example 1 was repeated except for using 2,2-bis[4-(4-maleimidophenoxy)-phenyl]propane in place of 2,2-bis[4-(4-maleimidophenoxy)-phenyl]1,1,1,3,3,3-hexafluoropropane. The properties of the resultings films were evaluated in the same manner as described in Example 1 and are listed in Table 1. Example 9 The process of Example 1 was repeated except for using a polyimide obtained from 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride and diaminodiphenylether in place of 50% of the polyimide used in Example 1. The properties of the resulting films were evaluated in the same manner as described in Example 1 and are listed in Table 1. Example 10 The process of Example 1 was repeated except for using a polyimide obtained from 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride and diaminodiphenylether in place of 50% of the polyimide used in Example 1, and using 6FDAPP-BMI of Example 2. The properties of the resulting films were evaluated in the same manner as described in Example 1 and are listed in Table 1. Example 11 The process of Example 1 was repeated except for using a polyimide obtained from 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride and diaminodiphenylether in place of 50% of the polyimide used in Example 1, and using 6FDAPP-BMI of Example 3. The properties of the resulting films were evaluated in the same manner as described in Example 1 and are listed in Table 1. Example 12 The process of Example 1 was repeated except for using a polyimide obtained from 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride and diaminodiphenylether in place of 50% of the polyimide used in Example 1, and using 6FDAPP-BMI of Example 4. The properties of the resulting films were evaluated in the same manner as described in Example 1 and are listed in Table 1. Example 13 The process of Example 1 was repeated except for using bis(3-ethyl-4-maleimido-5-methylphenyl)methane in place of 6FDAPP-BMI. The properties of the resulting films were evaluated in the same manner as described in Example 1 and are listed in Table 1. Example 14 The process of Example 9 was repeated except for using bis(3-ethyl-4-maleimido-5-methylphenyl)methane in place of 6FDAPP-BMI. The properties of the resulting films were evaluated in the same manner as described in Example 1 and are listed in Table 1. Comparative Example 1 After dissolving 2,2-bis[4-(4-diaminophenoxy)phenyl]propane in N-methyl-2-pyrrolidone, an equal amount of 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride was added thereto so as to make the total solid content 30%. After polymerizing at room temperature with stirring, a varnish of poly(amic acid) was obtained (reduced viscosity 0.82 dl/g at 25°C in N-methylpyrrolidone). Then, bis(4-maleimidophenyl)methane was added to the poly(amic acid) varnish so as to make the total solid content 30%. The properties of the resulting films were evaluated in the same manner as described in Example 1 and are listed in Table 1. Comparative Example 2 The process of Example 1 was repeated except for using a polyimide (reduced viscosity 1.05 dl/g at 25°C in N-methylpyrrolidone) obtained from 3,3',4,4'-biphenylcarboxylic dianhydride and p-phenylenediamine in place of the polyimide of Example 1. The properties of the resulting films were evaluated in the same manner as described in Example 1 and are listed in Table 1. Comparative Example 3 After dissolving 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride in N-methyl-2-pyrrolidone, tolylene diisocyanate and 4,4'-diphenylmethanediisocyanate (61:37.5 in weight ratio) were added so as to make the ratio of acid anhydride to isocyanate 1:1 and to make the total solid content 30%. The resulting solution was heated at 40°C for 2.5 hours with stirring, and gradually heated to 90°C, and allowed to react at 90°C for 2 hours, followed by heating at 130°C for 20 hours with stirring to give a polyimide solution (reduced viscosity 1.13 dl/g at 25°C in N-methylpyrrolidone). The resulting solution was cooled to 60°C, followed by addition of N,N'-(methylene-p-phenylene)-bismaleimide in the same amount as the 4,4'-diphenylmethane diisocyanate to give a uniform resin solution. Films were formed from the resin solution, and the properties of the films were evaluated in the same manner as described in Example 1 and are listed in Table 1. In Table 1, the modulus of elasticity was measured before curing at 250°C and after curing at 300°C. As is clear from Table 1, the heat resistant adhesive films according to the present invention show a lower modulus of elasticity before curing (at 250°C), but show a higher modulus of elasticity (at 300°) after curing, with high values of breaking strain and breaking strength. Further, the heat resistant adhesive films according to the present invention are also excellent in adhesiveness to copper and other polyimides. Example 15 A process for producing a thin film wiring board is explained. A one side copper-clad polyimide film (MCF 5000I, a trade name, mfd. by Hitachi Chemical Co., Ltd., thickness of copper 18 µm, thickness of polyimide 25 µm) was subjected to patterning by lithography to form a wiring pattern. The polyimide film having a pattern thereon was subjected to a plasma treatment and laminated on a mullite substrate via an adhesive film obtained in Example 1 (thickness 25 µm) using a mask aligner for fitting the position, followed by pressing with heating at 280°C for 60 minutes in an autoclave. Then, bore holes were formed at predetermined positions using an excimer laser. Then, metallic copper was deposited by electroless plating after a lithographic step to connect the wiring on the polyimide film. The above-mentioned process was repeated to form a thin film 6-layered wiring board. The resulting thin film wiring board was dipped in a solder bath heated at 330°C for 10 minutes (heat resistance test), but no change was found. Example 16 The process of Example 15 was repeated except for using the adhesive film obtained in Example 5 (25 µm thick) in place of that of Example 1. The resulting thin film wiring board showed no change in the same heat resistance test as in Example 15. Example 17 The process of Example 15 was repeated except for using the adhesive film obtained in Example 7 (25 µm thick) in place of that of Example 1. The resulting thin film wiring board showed no change in the same heat resistance test as in Example 15. Example 18 The process of Example 15 was repeated except for using the adhesive film obtained in Example 9 (25 µm thick) in place of that of Example 1. The resulting thin film wiring board showed no change in the same heat resistance test as in Example 15. Example 19 The process of Example 15 was repeated except for using the adhesive film obtained in Example 10 (25 µm thick) in place of that of Example 1. The resulting thin film wiring board showed no change in the same heat resistance test as in Example 15. Example 20 The process of Example 15 was repeated except for using the adhesive film obtained in Example 13 (25 µm thick) in place of that of Example 1. The resulting thin film wiring board showed no change in the same heat resistance test as in Example 15. Example 21 The process of Example 15 was repeated except for using the adhesive film obtained in Example 14 (25 µm thick) in place of that of Example 1. The resulting thin film wiring board showed no change in the same heat resistance test as in Example 15. Example 22 On a polyimide film of a thickness of 25 µm, underlying copper of 1000 Å in thickness was formed by evaporation, followed by coating of a photoresist thereon. After exposure to light and development on the predetermined portions, copper was deposited (20 µm thick) on the predetermined portions on the wiring by electric plating to obtain a stud for electrically connecting to upper layer wirings. Further, the underlying copper was removed by etching to give a wiring pattern. On the resulting wiring pattern, the adhesive film (40 µm thick) obtained in Example 2 was placed and pressed with heating under the same conditions as in Example 15 to obtain a stud burying the wiring therein. The surface of the adhesive film was polished to expose the stud portion to give a first layer wiring film. The process mentioned above was repeated to give a three-layered thin film wiring board. The resulting thin film wiring board was subjected to the heat resistance test by dipping in a solder bath at 330°C for 10 minutes. No change was found. Comparative Example 4 The process of Example 15 was repeated except for using the adhesive film obtained in Comparative Example 1 (25 µm thick) in place of that of Example 1. When the resulting thin film wiring board was subjected to the heat resistance test by dipping it in a solder bath at 330°C, blisters were formed within 10 seconds. Comparative Example 5 The process of Example 15 was repeated except for using the adhesive film obtained in Comparative Example 3 (25 µm thick) in place of that of Example 1. When the resulting thin film wiring board was subjected to the heat resistance test by dipping it in a solder bath at 330°C, blisters were formed within 10 seconds. As mentioned above, the thin film wiring board of the present invention is excellent in heat resistance at high temperatures, and thus can be directly mounted on LSIs and chip carriers. Further, the thermosetting resin composition of the present invention can be used as insulating materials for electronic parts, and the like.

Claims: Thermosetting resin composition comprising (A) a polyimide component comprising or consisting of: a thermosetting polyimide having repeating units of the formula I wherein are: R an alkyl group, a fluorinated alkyl group, an alkoxy group, a fluorinated alkoxy group, or a halogen atom; n 0, 1 or 2, and m 0 or an integer of 1 to 4, the polyimide having repeating units of the formula I being present in an amount of 30 % by weight or more, and preferably 50 % by weight or more, based on the weight of the polyimide component (A), and (B) a bismaleimide compound of the formula II wherein Ar is a divalent organic group having at least two carbon atoms. The thermosetting resin composition according to claim 1, showing a modulus of elasticity of 10 2 to 10 7 dyne/cm 2 in the course of heat curing. The composition according to claim 1 and/or 2, wherein the bismaleimide compound (B) is represented by the formula III wherein R 1 through R 6 are independently H, CH 3 , C 2 H 5 , C 3 H 7 , F, CF 3 , C 2 F 5 or C 3 F 7 ; and m is zero or an integer of 1 to 4, and the individual indices m may be the same or different. The composition according to one or several of claims 1 to 3, wherein the components (A) and (B) are mixed in amounts of 100 parts by weight of the component (A) and 50 to 200 parts by weight of the component (B). The composition according to one or several of claims 1 to 4, wherein component (A) is prepared by reacting pyromellitic dianhydride with diamino diphenyl ether in an organic solvent. The composition according to one or several of claims 1 to 5, wherein the polyimide component (A) comprises or consists of: (a) a polyimide having repeating units of the formula V and (b) a polyimide having repeating units of the formula VI The composition according to one or several of claims 1 to 6, wherein the polyimide component (A) further comprises a polyimide having repeating units of the formula IV wherein R and n are as defined in claim 1, the polyimide having repeating units of the formula IV being preferably present in an amount of 1 to 20 % by weight, based on the total weight of the polyimide component (A). The composition according to one or several of claims 1 to 7, wherein the polyimide is obtained by adding a poly(amic acid) to the bismaleimide (B), followed by imidization. Thermosetting resin composition, comprising (A') a poly(amic acid) component comprising or consisting of a poly(amic acid) obtained by reaction of a tetracarboxylic acid anhydride of the formula VII wherein R is an alkyl group, a fluorinated alkyl group, an alkoxy group, a fluorinated alkoxy group, or a halogen atom, and n is 0, 1 or 2, with a 4,4'-diaminodiphenyl ether of the formula VIII wherein R is as defined above, and m is 0 or an integer of 1 to 4, and (B) a bismaleimide compound of the formula II wherein Ar is a divalent organic group having at least two carbon atoms. The thermosetting resin composition according to claim 9, wherein the bismaleimide compound (B) is represented by the formula III wherein R 1 through R 6 are independently H, CH 3 , C 2 H 5 , C 3 H 7 , F, CF 3 , C 2 F 5 or C 3 F 7 ; and m is zero or an integer of 1 to 4, and the individual indices m may be the same or different. The thermosetting resin composition according to claim 9 and/or 10, wherein the poly(amic acid) component (A') comprises or consists of (a') a poly(amic acid) obtained by reaction of pyromellitic dianhydride with 4,4'-diaminodiphenyl ether and (b') a poly(amic acid) obtained by reaction of 3,3',4,4'-tetracarboxybenzophenone with 4,4'-diaminodiphenyl ether. The thermosetting resin compositions according to one or several of claims 9 to 11, wherein the poly(amic acid) component (A') further comprises a poly(amic acid) obtained by reaction of the tetracarboxylic acid anhydride of formula VII as defined in claim 9 with 4,4'-diaminodiphenylether-3-carbonamide of the formula preferably in an amount of 0.01 to 0.2 equivalent weight per equivalent weight of the tetracarboxylic dianhydride. The resin compositions according to claims 1 to 12, wherein the components (A) and (B), or the components (A') and (B), respectively, are present in the form of a mixture thereof. The resin compositions according to claims 1 to 12, wherein the components (A) and (B), or the components (A') and (B), respectively, are present separately in the form of a kit of parts, one part comprising component (A) or (A'), and the other part comprising the component (B). Thin film wiring boards comprising a plurality of base films having wiring patterns thereon and one or more adhesive layers placed between the base films, wherein the adhesive layers are made from a thermosetting resin composition according to one or several of claims 1 to 14. Thin film wiring boards according to claim 15, wherein the polyimide is obtained from a poly(amic acid) by imidization. Use of the thermosetting resin compositions according to claims 1 to 14 for manufacturing thin film wiring boards. Resin articles, obtained from the thermosetting compositions according to claims 1 to 14 by curing.

Inventors: MIWA TAKAO, NISHIMURA SHIN, OKABE YOSHIAKI, SATSU YUICHI, SUZUKI MASAHIRO, TAKAHASHI AKIO, MIWA, TAKAO, NISHIMURA, SHIN, OKABE, YOSHIAKI, SATSU, YUICHI, SUZUKI, MASAHIRO, TAKAHASHI, AKIO
Applicants: HITACHI CHEMICAL CO LTD, HITACHI LTD, HITACHI CHEMICAL COMPANY, LTD., HITACHI, LTD.
Application year: 1994
Main classification: C08L79
IPC codes: C08K5, H05K3, C08G73, H05K1, C08L79